Laurie Garrett says before American cruise missiles reach their targets, serveral diplomatic steps must be taken in order to stop the further use of nerve gases by the Syrian regime against its own people and prevent the use of chemical weapons from becoming the region's "new normal."

Global support for the "responsibility to protect" doctrine weakened after the UN-endorsed no-fly zone that helped topple Libya's regime, and debate continues over the threshold for mounting armed humanitarian interventions, explains this Backgrounder.

According to Micah Zenko, "We are deluding ourselves if we believe that we need more time to "think through" U.S. military intervention options for Syria. We have an excellent understanding of what those options are, and a vast majority of officials, policymakers, and the American people do not believe they are worth the effort."

A number of countries, including the United States, the United Kingdom, Turkey, and Qatar, have been providing support to the opposition in various forms, ranging from humanitarian aid to military supplies, such as weapons, armor, and communication devices. However, these efforts have not been enough to turn the tide, and after three years of fighting, a diplomatic solution still seems unlikely.

Michael Scott Doran and Max Boot lay out five reasons for why the United States should intervene in Syria, arguing that President Obama is forgoing his "lead from behind" approach where it would benefit the United States the most.

Intensification of the violence in Syria presents renewed cause for military intervention, either to protect innocent civilian lives or to potentially police or enforce a peace agreement or political settlement, says CFR's Paul Stares.

Stephen Zunes, Professor of Politics and Chair of Mid-Eastern Studies at the University of San Francisco, says rather than military intervention, nonviolent resistance combined with targeted international sanctions will force the Syrian government to negotiate with the opposition for a transfer of power to a democratic majority.